"It sounded like a Nazi air-raid siren," Agro recalled Tuesday. "It freaked me out. I knew it wasn't a ringtone."
The Hollywood couple -- and thousands of other smartphone owners in Florida -- had suddenly become acquainted with the latest way local, state and federal authorities are spreading the word about local emergencies.

In this case, it was a missing 2-year-old in Collier County.

"An AMBER Alert has been issued in your area, please check local media," the message read.

Fortunately, the child was found safe hours later, but not before many in Florida were left scratching their heads over how they received the disquieting alert without ever signing up for it.

The free alert -- with its unique alarm and vibration -- was sent through the federal government's Commercial Mobile Alert System, which has been sending out similar alerts to smartphones for several months. A congressional act in 2006 required all wireless carriers to manufacture phones capable of receiving such alerts by April 2012. The law calls for installing software on the phone that connects to the system and emits the alarming sound.

Buy a new cellphone lately Chances are you were automatically signed up for the alerts.

Since April, the system has been used mostly to warn citizens about imminent dangers such as tornadoes and hurricanes. It is also designed to send out emergency alerts from the president.

On Jan. 1, the National Center for Missing and Exploited Children joined the network and now sends out the Amber Alerts to wireless phones nationwide. It was the first time such an alert was sent out in Florida, said the center's program manager, Bob Hoever.

"The purpose of the Amber Alert is to rapidly notify the public as soon as possible when a child is facing danger," he said. "In this case, the wireless emergency alerts afford us [an opportunity] to reach a much wider audience."
In Florida, the Amber Alerts will still be issued by the Florida Department of Law Enforcement through emails and social media, among other means. But now the agency also will alert the national center so they can send out the wireless messages, said agency spokeswoman Gretl Plessinger.

The messages, transmitted through local cellphone towers, can be sent to a specific location, meaning even a person visiting South Florida from another state will receive the alert.

Customers may opt out of the alerts by changing their settings or calling their service provider. Alerts from the president, however, can't be declined, according to FEMA, which administers the program.

Monday's early morning Amber Alert in Florida became a widely discussed topic through social media, with many still confused over what they had received. Some supported it; others bemoaned being awakened in a panic.

"I didn't sign up but I'm happy I got it," wrote Facebook user Manuela Guntert Barson. "If it were my kid, I would want the whole world on the lookout."
Others complained that the alert didn't go far enough. Laura Esquivel, of Hollywood, said she spent more than an hour combing the Internet for more information about the missing child.

"I couldn't sleep that night. I kept wondering about the little girl and her family," she said.

That national center, however, is limited to only 90 characters and can't include other information, such as an Internet address or a full description of the missing child, officials explained.

Officials with the center decided on a policy to keep the messages simple while directing phone owners to seek more information through the local media.

Hoever sympathized with those who were roused from their deep sleep Monday, but he said it was necessary.

"We've had 602 children returned safely over the years because of the Amber Alert, and so you can see it's effective and we want to expand it," he said. "This helps us have more eyes and ears out there helping a missing child."
While many were surprised by Monday's alert, just as many were surprised about not receiving one.

Tammi Ruiz, of North Miami, said she got the alarm on her Verizon iPhone, but her husband's AT&T iPhone remained silent.

"I thought it was my WSVN alert, so I deleted it for waking me up," she said.

FEMA program manager Charles McCobb explained cellphone companies are still working out the kinks. The delivery of the messages depends on the service carrier, and in some cases, the phone itself, he said.

For example, a factory may have installed the software and enabled the alerts, but a different factory for the same type of phone may not have. Or a wireless company may have chosen to provide the alerts for a certain phone, but not the others. Wireless companies not providing the service must alert their customers, according to the federal law.

Currently, about 140 cellphone companies out of about 400 are distributing the alerts nationwide, including AT&T, Verizon and Sprint, said McCobb.

In most cases, an update to a phone's software should be enough, he said.

"It's slowly rolling in, and I would say if you were to buy a phone today, the chances are great that the software has already been installed," he said.

FDLE officials acknowledge many will try to opt out of the alerts, but hope that those people will sign up for less boisterous ways of receiving Amber Alerts, such as an email.

Free registration for the FDLE email alerts can be found at missingchildalert.com.

Social media coordinator Lori Todd contributed to this report.

ijrodriguez@tribune.com; 954-356-4605 or @GeoRodriguez on Twitter and Instagram
HOW TO
Sign up for smartphone alerts: Most phones manufactured in 2012 are built to automatically receive emergency alerts; upgrade to a newer system software; contact your wireless provider.